The present invention relates to ink jet printing and in particular discloses a buckle plate ink jet printer.
The present invention further relates to the field of drop on demand ink jet printing.
Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, xe2x80x9cNon-Impact Printing: Introduction and Historical Perspectivexe2x80x9d, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).
Ink Jet printers themselves come in many different types. The utilization of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
U.S. Pat. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al)
Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
Recently, in the proceedings of the IEEE Ninth Annual International Workshop on Micro-Electro Mechanical System, held in San Diego, Calif. on Feb. 11-15, 1996, there was presented a paper (pages 418-423 of the proceedings) entitled xe2x80x9cAn Ink Jet Head Using a Diaphragm Micro-actuatorxe2x80x9d, by Susumu Hirata et al. in which a form of ink jet head utilising a buckling diaphragm was described. The described ink jet head relied upon a diaphragm being heated so as to cause the diaphragm to buckle rapidly resulting in the ejection of ink from around the diaphragm, through a nozzle hole.
The aforementioned arrangement due to Hirata et. al. has a number of significant disadvantages. Firstly, the size of the necessary buckle plate as described is approximately 300 microns in diameter which is of an excessively large size, especially where, as is common, large arrays of ink jet nozzles are required. This is especially the case with a pagewidth printhead where many thousands of nozzles may need to be constructed for each colour outputted.
Further, the Hirata et al. arrangement utilizes an excessive amount of applied energy to the actuator. This is evident by the authors"" discussion on page 423 where they note that, as the frequency of operations increases, the temperature of the diaphragm rises to the point where the device is no longer properly operational.
It is an object of the present invention to provide an alternative arrangement of a buckle/diaphragm actuated ink jet print head, simple and compact in construction however, allowing for a higher speed operation of the ink jet head through the utilization of substantially less energy per ink drop ejected.
In accordance with a first aspect of the present invention there is provided an ink jet printing device of the type having at least one nozzle connected to an ink supply and having a buckle plate able to be deformed so as to eject ink on demand from the nozzle. The buckle plate can be constructed from a first material having a high coefficient of thermal expansion and from a second electrically resistive material for heating the buckle plate. Further the second material can have a lower coefficient of thermal expansion than the first material and is constructed in a serpentine manner so as to allow the expansion of the length of the heater means substantially in accordance with the expansion of the first material. Preferably the first material comprises substantially polytetrafluoroethylene and the second material comprises substantially copper. Further, the energy of activation of the buckle plate for the ejection of a drop of ink is less than about 20 microjoules and more preferably less than one microjoule.